Process for the recovery of volatile solvents



G. W. COGGESHALL AND T. IVI. RECTOR.

PROCESS FOR THE RECOVERY 0F voLAmE soLvENTs.

APPLICATION FILED MAR. Il| i920.

PatentedJune 6, 1922.

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NETE@ STATES GEORGE W. COGG-ESHALL AND THOMAS M. RECTOR, OF WASHINGTON, DISTRICT Olli` Parana erstes..

COLUMBIA, ASSIGNORS TO THE INSTITUTE 0F INDUSTRIAL RESEARCH, INC., 0F WASHINGTON, DISTRICT OF COLUMBIA, A CORPORATION OF THE DISTRICT OF COLUMBIA PROCESS FOR THE RECOVERY OF VOLATIL'E SOLVEN TS.

Specification of Letters Patent. Pwtmted Jun@ 69 19220 Application led March 11, 1920. Serial No. 365,104.

To all whom it may concern:

Be it known that we, (l) GEORGE W. Coe- GEsHALL and (2) THOMAS M. RECTOR, citizens of the United States, residing at Washington, in the District of Columbia, have vinvented certain new and useful Improvewhich it has been associated in any other manner, by passing a current of gas, such as air over the materlal, the gas being warmed to a temperature suiiicient to volatilize the solvent. The mixture of gas and solvent vapor is then brought into intimate contact with a suitable adsorbent, such as charcoal, iron-oxide, or, in particular, carbon which has been activated, as by heating and selective oxidation. The volatile vapors are adsorbed by the mass of adsorbent material.

t and the mass is then heated to volatilize the vent is removed from the mass of adsorbent in the same length of time than when no incondensible gas is so passed through. It has also been found to be advantageous to remove such gas from the condenser or collecting vessel, reheat it and again pass it through the heated adsorbent material. We

have found that we may use air `or other inert gas of greater molecular weight, such as CO2. A further improvement is obtained when inert non-oxidizing gas, such as CO2 for example, is used, which is that volatile solvents such for example as alcohol are not oxidlzed during the recovery process as often happens when air is circulated or no gas is circulated.

The mode of application of the invention will be understood from the accompanying description and drawing in which,-

F1g. l is a diagrammatic representation of the system;

-Fig 2 is a vertical cross section through the adsorber; and

Fig. 3 is a diagram of a modification. A

Referring to Fig. 1, 10 is a roll of textile or other material, which is fed to a coating device 11, where the coating dope, com-v prisin coating material dissolved in the volat1 e solvent, is applied to the textile material, the dope being supplied from a'l tank, 12.

The coated material through a drier tunnel, in which the volatile solvent is driven 0H from the coated material. by means of a current of heated air or other gas, supplied through pipe 36 from a suitable heater 14. The coated material passes out of the drier tunnel and is wound upon a roll, 15, or otherwise disposed of, in any well known way.

The mixture of volatile solvent and heated carrier gas, comingl from the drier or chamber in which the ymaterial has been heated to drive oif the solvent, passes through pipe 30, to a cooler 16, which may beof any suitable construction. In the cooler, the temperature of the mixture is lowered but not sufficient to cause condensation of the solvent vapor. From the cooler, 16, the mixed gas and vapors pass through pipe 17, provided with a valve A, to the adsorber 18, which .has an exitpipe 19, provided with valve E. -A pipe 20, having valve D therein, also connects exit pipe 19 to a condenser 21, from which the condensed solvent flows into receptacle 22. The branch pige 29, leads from pipe 17 to one or more ot er adsorbers and has a valve B.

The adsorber ma be made as shown in is then passed.

Fig 2. Within t e casing thereof, are

Je constructed and arranged that they will provide surfaces extending as far as possible ;hroughout the entire surrounding mass of tdsorbent, lthereby insuring that the whole nass is effectively heated or cooled, as the :onditions require. The form of hollow nember shown, is effective, but may obvi- )usly be varied in many other ways to obain the desired result.

The closed receptacle 22 serves as a sepalator for the gas and condensed solvent, the gas being led through pipe 31 to pump 32, leater 33 and pipe 34, having valve C to )i e 17, leading into the adsorber.

he operation is as follows The mixed gas and vapor, preferably after laving been cooled to a suitable degreev are assed through the adsorber Where they are roughtinto intimate contact'with the adorbent material. It has been` found to be enerally advantageous to keep the adsorbnt materia-l cool during this adsorbing opration, and, therefore, cold Water is passed hrough the members 26.

The volatile solvent is adsorbed by the ctivated carbon or other material While the arrier gas, passes out through exit 19, the alves A and E being open, and valves B and and-C being closed during this operation. VWhen the adsorbent material has taken up s much of the volatile solvent as it will or s is found precticable, the valves A and E re closed, valves B and D are opened, and eating fluid is supplied to the members 26, nbeddedin the adsorbent material. The lsorber solvent is thereby vaporized and 1e vapors are condensed in the condenser 21.

This volatilizatien is` further largely ssisted Dby the v current of circulating arm gas coming' from the heater 33 and issing up through pipe 34 into the adsorber, Llve C being then open.

In the meantime, another adsorber has ien connected through pipe 29, so that the covery Vof solvent is uninterrupted. We we found that when activated carbon is ed for adsorption, it is desirable to keep e mass cool, and that under proper condi- )ns the activated carbon will adsorb from l air-alcohol vapor mixture an amount of cohol almost e ual in Weight tothat of the rbon' itself. `When the chargedadsorber heated to about 150 ldily distils off. In Fig. 3, the pipe 35 conveying fresh air C., the alcohol vapor to heater 14 has a valve V, and heatedv air is delivered through pipe 36 to the driertunnel. A by-pass pipe 37 connects pipes 30 and 36, and is provided with a suctionblower 38 and a valve W.

The operation of this apparatus is as follows It has been found that in ordinary practice so much fresh air is passed through the drier that the concentration of solvent vapors in the air-vapor mixture issuing from the drier is low, and to reduce the volume of air, thereby increasing the vapor concentration, air-valve V is partly closed and air-valve W is partially or wholly opened so that with or without the assistance of the small air suction-blower 38, a certain portion of the heated air-vapor mixture issuing from the drier is passed through pipe 37 to pipe 36 and recirculated through the drier. The

result is to increase the concentration of solvent vapors in that portion of the heated air-vapor mixture entering the cooler 16 and passing on to the adsorber. A further result of this arrangement is that less total air is lieatedin 14, less air-vapor mixture cooled in 16, a more rapid and complete adsorption of solvent vapors is made in the adsorber and by proper regulation of valves V and W and regulation of the speed ofthe suction-blower 38, the concentration of solvent vapor in the air-vapor mixture passing to the adsorber may be controlled and at the same time a slight suction may be produced in the drier in lace of a slight air-presn sure. This circu ating system may be used independently of orin conjunction With that shown in Fig. 1. A slight suction prevents escape of air-vapor mixture into the workroom with its resultant disadvantages, not the least of which is the fire danger. Another suction blower 38, located in pipe 17, may be used,` if desired.

he invention is in no way limited to the particular apparatus shown, and changes may be made therein Without departing from the spirit of the invention. While we have referred to alcohol, obviously any other volatile solvents, Whose vapors are capable of adsorption or occlusion, by solid materials of the kind referred to, can be recovered 'by the process described.

We claim:

1. The method of recovering condensable volatile solvents which have been adsorbed on solid materials with subsequent heating to drive off the adsorbed vapors characterized by this that during the heating a current of incondensable gas is assed over the adsorbent, the resulting mixed gas and vapor being passed through a condenser to condense said solvent and the incondensable gas being returned from the condenserand the adsorber during the heating operation.

2. The process as claimed in claim 1 in 130 Leisee ous mixture Which comprises circulating a portion of said mixture over'said material,` 10

and then passing the enriched gaseous mixture over solid material capable of adsorbing the vapors.

In testimony whereof, We afx our signatures.

GEORGE W. COGGESHALL. THOMAS M. RECTOR. f 

